Tissue elasticity is universally recognized as a diagnostic and prognostic biomarker for prostate cancer. As the first diagnostic test, the digital rectal examination is used since malignancy changes the prostate morphology and affects its mechanical properties. Currently, this examination is performed manually by the physician, with an unsatisfactory positive predictive value of 42%. A more objective and spatially selective technique is expected to provide a better prediction degree and understanding of the disease. To this aim, here we propose a miniaturized probe, based on optical fiber sensor technology, for mechanical characterization of the prostate with sub-millimeter resolution. Specifically, the optical system incorporates a customized Fiber Bragg Grating, judiciously integrated in a metallic cannula and moved by a robotic arm. The probe enables the local measurement of the force upon tissue indentation with a resolution of 0.97 mN. The system has been developed in such a way to be potentially used directly in vivo. Measurements performed on phantom tissues mimicking different stages of the prostatic carcinoma demonstrated the capability of our device to distinguish healthy from diseased zones of the prostate. The study on phantoms has been complemented with preliminary ex vivo experiments on real organs obtained from radical surgeries. Our findings lay the foundation for the development of advanced optical probes that, when integrated inside biopsy needle, are able to perform in vivo direct mechanical measurements with high sensitivity and spatial resolution, opening to new scenarios for early diagnosis and enhanced diagnostic accuracy of prostate cancer.
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